During some decades, well tests have allowed to determine some reservoir characteristics such as the formation permeability (assumed to be constant), the skin factor, the reservoir pressure. However, there are few methods for refining reservoir models by integrating both production data and well tests. One reason for this phenomenon is that the well testing technology is especially based on analytical solutions that are not directly compatible with the discrete representations used for the models in reservoir simulation.
With the advent of numerical flow simulators, it appeared that well tests can contribute to refining the description of the geological model: spatial distribution of the permeability values, boundary distance estimation, etc. A flow simulator is software allowing, among other things, to model the production of a reservoir as a function of time, from measurements describing the reservoir, i.e. from a reservoir model.
Considering that there is no method suited for simultaneous integration of well tests and production data in numerical reservoir models, a conventional technique consists in matching the well test data using the same approach as for matching the production data, but separately. Such a technique is for example described in the following document:                Mezghani, M., 1999, <<Caractérisation des réservoirs hétérogènes: méthode des sentinelles et quantification des incertitudes>>, Ph.D. thesis, Univ. Paul Sabatier, Toulouse, France.        
It consists in entering as the input data, in software referred to as flow simulator, the flow rate data, in simulating the pressures and in comparing them with the pressures measured during the well test. The parameters of the model are then modified as long as pressure matching is not satisfactory.
There is also a known method for simultaneously matching the pressures, the pressure derivatives and the production data:                Landa, J. L., 1997, Reservoir parameter estimation constrained to pressure transients, performance history and distributed saturation data, Ph.D. thesis, Stanford Univ., Stanford, Calif.        
According to this approach, the production data and the well tests are simulated at the same scale, i.e. the reservoir scale. Now, the well tests correspond to a finer scale than the reservoir scale.
Finally, there is another known method, called NWT (Numerical Well Testing). This method is described in:                Kamal, M. M., Pan, Y., Landa, J. L., and Thomas, O. O., 2005, “Numerical well testing —A method to use transient testing results in reservoir simulation”, SPE 95905, Dallas, Tex.        
The drawback of the NWT method is that well test matching and production data matching are dissociated.
The object of the invention thus is an alternative method for optimizing the development of underground reservoirs, by constructing a geological model representative of the reservoir, meeting dynamic data and well tests.